Application of gas chromatography/mass spectrometry instrument techniques to forensic urine drug testing.

Appropriate GC/MS analytical techniques can provide conclusive confirmatory evidence for the presence of drugs and metabolites in forensic urine drug testing. Although forensic laboratories are required to utilize GC/MS, they have flexibility in selecting instrumentation, modes of operation, and actual analytical methods. Because a laboratory's accreditation status, reputation, and economic well-being depend on consistently accurate results, it is important to use optimal analytical procedures so that reliability and accuracy are maximized. Pitfalls in conventional EI SIM techniques can lead to high rates of false-positive and false-negative results. Different mass spectrometric operating modes such as CI and full-scan can be used to complement SIM analyses. These modes are useful in solving difficult identification problems and in enhancing both specificity and sensitivity. Newer types of GC/MS systems based on ion trapping offer the promise of technologic advances in enhanced analytical performance and productivity gains. Knowledge of the advantages and potential pitfalls of different GC/MS systems as well as different ionization and detection modes is helpful in optimizing the accuracy of compound identification.